class_docstr: A column object, with only the methods and properties required by the
  interchange protocol defined.
  A column can contain one or more chunks. Each chunk can contain up to three
  buffers - a data buffer, a mask buffer (depending on null representation),
  and an offsets buffer (if variable-size binary; e.g., variable-length
  strings).
  Note: this Column object can only be produced by ``__dataframe__``, so
        doesn't need its own version or ``__column__`` protocol.
docstr: Return the buffer containing the mask values indicating missing data and
  the buffer's associated dtype.
  Raises NoBufferPresent if null representation is not a bit or byte mask.
docstr_tok: ["Return","the","buffer","containing","the","mask","values","indicating","missing","data","and","the","buffer","'s","associated","dtype",".","Raises","NoBufferPresent","if","null","representation","is","not","a","bit","or","byte","mask","."]
code: def _get_validity_buffer(self) -> tuple[PandasBuffer, Any]:
      """
      Return the buffer containing the mask values indicating missing data and
      the buffer's associated dtype.
      Raises NoBufferPresent if null representation is not a bit or byte mask.
      """
      null, invalid = self.describe_null
  
      if self.dtype[0] == DtypeKind.STRING:
          # For now, use byte array as the mask.
          # TODO: maybe store as bit array to save space?..
          buf = self._col.to_numpy()
  
          # Determine the encoding for valid values
          valid = invalid == 0
          invalid = not valid
  
          mask = np.zeros(shape=(len(buf),), dtype=np.bool_)
          for i, obj in enumerate(buf):
              mask[i] = valid if isinstance(obj, str) else invalid
  
          # Convert the mask array to a Pandas "buffer" using
          # a NumPy array as the backing store
          buffer = PandasBuffer(mask)
  
          # Define the dtype of the returned buffer
          dtype = (
              DtypeKind.BOOL,
              8,
              ArrowCTypes.BOOL,
              Endianness.NATIVE,
          )
  
          return buffer, dtype
  
      try:
          msg = f"{_NO_VALIDITY_BUFFER[null]} so does not have a separate mask"
      except KeyError:
          # TODO: implement for other bit/byte masks?
          raise NotImplementedError("See self.describe_null")
  
      raise NoBufferPresent(msg)
  
imports: from __future__ import annotations
  from typing import Any
  import numpy
  from pandas._libs.lib import infer_dtype
  from pandas._libs.tslibs import iNaT
  from pandas.errors import NoBufferPresent
  from pandas.util._decorators import cache_readonly
  from pandas.core.dtypes.dtypes import ArrowDtype, DatetimeTZDtype
  import pandas
  from pandas.api.types import is_string_dtype
  from pandas.core.interchange.buffer import PandasBuffer
  from pandas.core.interchange.dataframe_protocol import Column, ColumnBuffers, ColumnNullType, DtypeKind
  from pandas.core.interchange.utils import ArrowCTypes, Endianness, dtype_to_arrow_c_fmt
label_desc: Use image node_id 14 for calling the PandasColumn obj's underlying member method code with example usage: obj._get_validity_buffer() and returns: buffer,  dtype